This invention relates to the repair of components of turbine engines, for example repair of a vane segment of a turbine engine. More particularly, it relates to the repair of a gas turbine engine turbine vane segment which has experienced high temperature operation in the engine.
During operation in the hot section of a gas turbine engine, portions of air cooled vane segments which have been assembled into a vane assembly, sometimes called a nozzle or nozzle assembly, can become damaged to the point at which replacement or repair is required to maintain safe, efficient engine operation. Because such air cooled components are complex in design, are made of relatively expensive materials, and are expensive to manufacture, repair is the desired choice. The capability for repeating the repair, if necessary after subsequent operation, is a highly desirable goal for any such repair method.
Various repair methods and apparatus have been widely reported and used for many years in the gas turbine engine art. One example is U.S. Pat. No. 4,305,697--Cohen et al., patented Dec. 15, 1981, relating to the repair of a gas turbine engine air cooled vane segment. One example of a gas turbine nozzle showing, among other things, the axial, radial, and circumferential positioning of the nozzle and its members in respect to the engine is described in U.S. Pat. No. 5,343,694--Toborg et al., patented Sep. 6, 1994. Identified in such patents are typical vane assemblies to which this invention also relates. The disclosure of each of such patents hereby is incorporated herein by reference.
During repair of such a vane segment, one or more of the components of the segment are removed and replaced. Frequently, at least the airfoil is replaced because of its exposure to strenuous airflow and high temperature operating conditions. Replacement of an entire member of the segment, such as one or more entire airfoils, requires precise relocation of the replacement part in respect to other members of the segment to provide between the members the relationship originally designed to enable proper airflow through the vane segment. That relationship between the members of a vane segment is referred to herein as the designed relationship.
In addition to the problem of precise relocation of the members which comprise the vane segment is the requirement to regenerate, such as by machining, certain important vane segment features which are filled, covered or distorted during repair. Typical of such features are seal slots at circumferential borders of segment platforms. Known repair methods typically fill such seal slots with brazing alloy or other additional material during repair, requiring remachining of such slots after reassembly of the repaired segment.